Method of drying hermetically enclosed refrigerating machines via special vapors



Jan. 19, 1965 A. F. ENEMARK ETAL 3,

METHQD 0F DRYING HERMETICALLY ENCLOSED REF RIGERATING MACHINES VIA SPECIAL VAPORS Filed Aug. 21, 1961 ZONE I ZONE 2 \L HEATER United States Patent METHQD 0F DRYING HERMETECALLY EN- CLOSED REFRIGERATING MACHKNES VlA SPECIAL VAPORS Arne Fromm Enemarlr, Sonderhorg, and Gunner Serenesen and Gustav Adoll Johansson, Nordborg, Denmark, assignors to Danfoss vetl ing. M. Clausen, Nordhorg, Denmark, a company of Denmark Filed Aug. 21, 1961, Ser. No. 134,042 7 Claims. (Cl. 134-31) The method of drying hermetically enclosed refrigerating machines and other units in a vacuum is already known. This method, however, involves considerable expense.

For the purpose in question the general practice is to use hot air as a dehydrating agent and to carry the unit through a drying oven. At a temperature of the dry air of 150 C. to 160 C., drying of an enclosed compressor unit will take from 6 to 12 hours. For this reason the drying process becomes a bottleneck in the production of refrigerating machines.

It is possible, however, to cut down somewhat the time of drying by heating the stator winding of the motor during its passage through the drying oven. To prevent damage to the winding, however, a very close supervision of the temperature is required, and facilities for connection of electric current to the moving conveyor belt in the drying oven must be provided. It has also been necessary to be sure that all units inserted for drying were fitted with the same type of motor, or else, the heating eflect would be different, and providing temperature regulation for each particular motor would be a disregard of expense.

A drawback in the conventional method of drying is that the finished unit has to be dried prior to carrying out the trial run which is necessary for determining defects, if any. The reason for this is that oil will decompose during drying in a vacuum or in hot air and may leave a residue in the system, which' can result in clogging of the valves and the capillary tube, and in undesired chemical reactions.

Another drawback in connection with the hot air drying method is that a certain percentage of humidity will remain in the system, even in the case of long-time drying. .In the case of refrigerant equipment in particular,

where a high degree of dryness is essential, this humidity can be a source of error.

- The method forming the subject of the present invention provides several measures which taken as a whole and in each particular case will considerably improve the known method of drying, and together lead to a method in which the above mentioned drawbacks will be eliminated.

For the purpose of the present invention, the dehydrating agent shall be a greaseand oil-dissolving fluid. Thus, this dehydrating agent is able to remove at the same time the two disturbing factors from a refrigerant system,

viz., water, which through the formation of ice may result in clogging and other faults, and oil, which through chemical decomposition may form small, disturbing foreign bodies.

Owing to these measures it is possible to provide the finished unit on the conveyor belt with oil and to carry out trial runs. During these tests it can be ascertained whether there are still any defects to be remedied. In the end, the oil is simply poured out, and any remnants of oil will be without influence since they will be removed during drying.

To achieve the second purpose of the present invention a dehydrating agent is used which will condense when flowing through the unit- In general, the condensed fluid 3,l%,445 Patented Jan. 19, 1965 will more easily drive out the oil than will steam. Further, the oil dissolved in the condensate will readily drip away from the unit. At the same time, condensation of the dehydrating agent has the advantage that heat given up during the process of condensation in a short period of time will develop the required drying temperature in the unit to be dried.

To achieve the third purpose of the present invention, a dehydrating agent is used which to the greatest possible extent will displace water vapor. This can be achieved by so choosing the dehydrating agent, the drying temperature and the volume of the drying oven, that the partial pressure of the dehydrating vapor is considerably higher than the partial pressure of the water vapor. By keeping the ratio of the partial pressures the same as that of the weight or volume parts of the respective vapors, the drying process will in the end result in a considerably smaller amount of humidity in the units put up for drying, than would have been the case if air had been used for drying.

It will be most expedient to carry out the method forming the subject of the present invention in a two-step working program, in which the units to be dried are first carried through a zone in the drying oven with saturated vapor, and thereupon through a zone with superheated vapor. In the first zone the unit is rapidly heated by the condensed vapor at the same time as remnants of oil and grease are loosened and washed off. In the second zone the drying effect proper can be increased by raising the temperature.

There is also the possibility of using hot air or nitrogen as the superheated vapor in the second zone. Through this method the dehydrating agent used in the first zone is removed. In general such dehydrating agents are more easily removed by hot air than by water vapor. Further, it will be possible to use a dehydrating agent in the first zone which may have a harmful influence. upon certain parts of the unit, such as to soften the refrigerant proof insulating lacquer. This is possible because the time of exposure to the harmful influence is limited, and very often, after-treatment with hot air will result in an improvement of the original conditions, such as an addi- .in the unit. After the unit has been relieved of pressure, only a negligible quantity will remain.

The boiling point of the oil and grease dissolving dehydrating agent is at least C., and the agent must retain its chemical properties at a temperature of about 200 C.

First of all, perchloroethylene should be considered as adehydrating agent, because it possesses all the above mentioned properties essential to the invention. Especially its boiling point of 119 C. is well above that of water. It will, be possible, however, to employ other dehydrating agents, suchas trichloroethylene.

Additional characteristics of the invention will appear from the following description of an example of employing the method forming the subject of the present invention.

area res with oil, and submitted to a trial run to ascertain whether there are any defects or shortcomings. After the trial run the cover is removed, and the capsule is turned with its opening downwards to permit the oil to drain off. In this position the capsule is then carried through a drying oven by means of a conveyor belt.

The first zone of this oven contains vapor of perchloroethylene in which vapor the unit remains for to minutes. In the bottom of the oven liquid perchloroethylene is heated to the boiling point. The walls of the oven are cooled so that the vapor will complete a cycle. The perchloroethylene vapor has a temperature of 119 C. and will condense immediately on all parts of the units inserted for drying, until these units in the course of about 5 minutes have been heated nearly to the same temperature. The condensed perchloroethylene drips down from the unit, carrying with it dissolved oil and grease. At the same time the perchloroethylene will force the water vapor out of all cavities of the unit, so that the unit, when transferred from the first zone of the oven to the second zone, contains a predominant content of perchloroethylene vapor and but a small content of water vapor.

The second zone of the oven contains dry air at a temperature of 150 C. to 160 C. The unit remains in this atmosphere for about minutes. The perchloroethylene vapor is easily and quickly forced out of the unit by the hot air. As the unit has already attained a temperature of about 119 C., heating to a further 30 C. takes place in a comparatively short time. Taken as a whole, the measures described above render it possible to cut down the process of drying from 6 to 12 hours to about minutes.

After this process has been completed, the unit is hermetically enclosed and the hermetically enclosed unit is submitted to a conventional pressure test with dry air at a pressure of 5 atmospheres, for example. While still under pressure, the capsule may be carried through another oven, for example a lacquer drying oven, and thereafter the pressure is relieved. By this procedure the contents of perchloroethylene in the unit is further reduced. This measure, however, is merely considered an additional safety measure, since only a very little and harmless trace of water and perchloroethylene will be left in the unit at the end of the drying process. A test showed as little a content of water as .05 parts per million.

The dehydrating agent 5 should as mentioned have a boiling point of at least 75 C. at atmospheric pressure. In addition it should be liquid at room temperature and should not decompose at the highest temperature used in the drying process, e.g., 150 C. and should not have any adverse action on the electrical insulation or form any acid when in contact with water vapor of the process or during the lifetime of the unit, e.g., sulphuric acid which lead to copper plating. A particularly suitable class of solvents meeting these criteria are the chlorinated hydrocarbons boiling between 75 C. and 150 C. at atmospheric pressure, and especially suitable are the perchloroethylene and trichloroethylene mentioned, but it is in the scope of the invention to use other liquids, e.g. when other insulation is used for the electrical insulation. The solvents mentioned are satisfactory with papers and Mylar insulation.

What we claim and desire to secure by Letters Patent is:

1. A method of dehydrating and degreasing the mechanism of a hermetically-enclosed refrigeration machine which comprises, assembling a motor-compressor unit comprising a motor having electrical windings and a hermetic enclosure, adding a lubricant to said unit and test running the motor-compressor unit without the enclosure being permanently hermetically sealed, removing the lubricant from said unit, exposing said unit including said electric motor while a part of the hermetic enclosure is removed therefrom, to the action of a first normallyliquid dehydrating first agent which is a grcase-and-oildissolving fluid, in a treating zone; said fluid being brought into contact with said unit in heated vapor form, and subsequently exposing said unit while a part of the hermetic enclosure is removed therefrom in a second treating zone to a second normally-gaseous dehydrating agent maintained at a temperature for drying said unit.

2. A method according to claim 1, in which said first agent is selected from the group comprising perchloroethylene and trichloroethylene.

3. A method of drying the mechanism of a hermetically-enclosed refrigeration machine which comprises, assembling a motor-compressor unit comprising a motor having electrical windings and a hermetic enclosure, adding a lubricant to said unit and test running the motorcompressor unit without the enclosure being permanently hermetically sealed, removing the lubricant from said unit, exposing said unit including said electric motor While a part of the hermetic enclosure is removed therefrom to the action of a first normally-liquid dehydrating first agent which is a grease-and-oil-dissolving fluid in a treating zone, said fluid being brought into contact with said unit in heated vapor form, subsequently exposing said unit while a part of the hermetic enclosure is removed therefrom in a second treating zone to a second normallygascous dehydrating agent maintained at a temperature for drying said unit, and said first agent having a boiling point higher than that of water and retaining its properties at a temperature of about 200 C.

4. A method of drying the mechanism of a hermeticallyenclosed refrigeration machine which comprises, assembling a motor-compressor unit comprising a motor having electrical windings and a hermetic enclosure, adding a lubricant to said unit and test running the motor-compressor unit without the enclosure being permanently hermetically sealed, removing the lubricant from said unit, exposing said unit including said electric motor while a part of the hermetic enclosure is removed therefrom to the action of a first normally-liquid dehydrating first agent which is a grease-and-oil-dissolving fluid in a treating zone, said fluid being brought into contact with said unit in heated vapor form, subsequently exposing said unit while a part of the hermetic enclosure is removed therefrom in a second treating zone to a second normallygaseous dehydrating agent maintained at a temperature for drying said unit, and said first dehydrating agent being applied in said first zone with a partial pressure of the vapor of the dehydrating agent considerably higher than the partial pressure of water vapor.

5. A method of drying the mechanism of a hermeticallyenclosed refrigeration machine which comprises, assembling a motor-compressor unit comprising a motor having electrical windings and a hermetic enclosure, adding a lubricant to said unit and test running the motorcompressor unit without the enclosure being permanently hermetically sealed, removing the lubricant from said unit, exposing said unit including said electric motor while a part of the hermetic enclosure is removed therefrom to the action of a first normally-liquid dehydrating first agent which is a grease-and-oil-dissolving fluid in a treating zone, said fluid being brought into contact with said unit in heated vapor form, subsequently exposing said unit while a part of the hermetic enclosure is removed therefrom in a second treating zone to a second normallygaseous dehydrating agent maintained at a temperature for drying said unit, and said second agent being selected from the group consisting of dry air and an inert gas.

6. A method of drying the mechanism of a hermetically-enclosed refrigeration machine which comprlses, assembling a motor-compressor unit comprising a motor having electrical windings and a hermetic enclosure, adding a lubricant to said unit and test running the motorcompressor unit without the enclosure being permanently hermetically sealed, removing the lubricant from said unit, exposing said .nnit including said electric motor while a part of the hermetic enclosure is removed therefrom to the action of a first normally-liquid dehydrating agent which is a grease-andoil-dissolving fluid in a treating zone, said fluid being brought into contact with said unit in heated vapor form, subsequently exposing said unit while a part of the hermetic enclosure is removed therefrom in a second treating zone to a second normallygaseous dehydrating agent maintained at a temperature for drying said unit, said first dehydrating agent being,

applied in said first zone with a partial pressure of the vapor of the dehydrating agent considerably higher than t hermetically sealed, removing the lubricant from said unit,

exposing said unit, including said electric motor while a part of the hermetic enclosure is removed therefrom to the action of afirst normally-liquid dehydrating agent I which is a grease-and-oil dehydrating fluid in a first treating zone, said fluid being brought into contact with said unit in heated vapor form for condensing it on said unit, subsequently exposing said unit while a part of the hermetic enclosure is removed therefrom in a second treating zone to a second normally-gaseous dehydrating agent maintained at a temperature for drying said unit and said unit being held in said first zone in position for the condensed first agent together with the oil and grease dissolved by said first agent to drain off.

References Cited by the Examiner UNITED STATES PATENTS 2,096,736 10/37 Dinley 134-11 2,220,125 11/40 Seaton 1341 1 21,557,621 6/51 Touborg 34-37 2,557,915 12/51 Piller 3436 I FOREIGN PATENTS 548,116 9/42 Great Britain. 551,559 3/43 Great Britain.

NORMAN YUDKOFF, Primary Examiner.

GEORGE D. MITCHELL, Examiner. 

1. A METHOD OF DEHYDRATING AND DEGREASING THE MECHANISM OF A HERMETICALLY-ENCLOSED REFRIGERATION MACHINE WHICH COMPRISES, ASSEMBLING A MOTOR-COMPRESSOR UNIT COMPRISING A MOTOR HAVING ELECTRICAL WINDINGS AND A HERMETIC ENCLOSURE, ADDING A LUBRICANT TO SAID UNIT AND TEST RUNNING THE MOTOR-COMPRESSOR UNIT WITHOUT THE ENCLOSURE BEING PERMANENTLY HERMETICALLY SEALED, REMOVING THE LUBRICANT FROM SAID UNIT, EXPOSING SAID UNIT INCLUDING SAID ELECTRIC MOTOR WHILE A PART OF THE HERMETIC ENCLOSURE IS REMOVED THEREFROM, TO THE ACTION OF A FIRST NORMALLYLIQUID DEHYDRATING FIRST AGENT WHICH IS A GREASE-AND-OILDISSOLVING FLUID, IN A TREATING ZONE; SAID FLUID BEING BROUGHT INTO CONTACT WITH SAID UNIT IN HEATED VAPOR FORM, AND SUBSEQUENTLY EXPOSING SAID UNIT WHILE A PART OF THE HERMETIC ENCLOSURE IS REMOVED THEREFROM IN A SECOND TREATING ZONE TO A SECOND NORMALLY-GASEOUS DEHYDRATING AGENT MAINTAINED AT A TEMPERATURE FOR DRYING SAID UNIT. 